Irish Mail cancelled at the post office counters still provides an opportunity for interesting and challenging cancels, especially since many smaller towns in the Irish /Celtic language are not easily found, even if they are clear and complete enough to read. This one got an immediate "hit" on an internet search.
CATHAIR NA MART
05. 9. 18
This is The cancellation of town formerly known as Westport (ca 1780), population 6198.
From wikipedia, "Westport (Cathair na Mart, meaning 'city of the beef cattle', historically anglicized as Cathernamart) is a town in County Mayo in Ireland. It is at the south-east corner of Clew Bay, an inlet of the Atlantic Ocean on the west coast of Ireland."